As if the risk of heart disease was not enough, men now have another incentive to monitor their fat intake with the release this week of a Harvard Medical School study that found that high levels of saturated fats could damage their sperm.

According to the study, an increased intake of saturated fats and monounsaturated fats—which are commonly found in meats, butter, and dairy products—may result in a lower sperm concentration.

But the research also suggests that increasing consumption of polyunsaturated fats may have the opposite effect. The study found that omega-3 fatty acids, primarily those found in fish fats, are associated with improved sperm motility and morphology, which relate to sperm movement and the size and shape of the sperm.

According to the study’s lead researcher, Jill A. Attaman, who is an instructor in Obstetrics, Gynecology and Reproductive Biology at the Medical School, the results may impact men in different ways. The study indicates that those with a marginal sperm concentration may see more of an effect than men who have a higher sperm count to begin with, she said.

“Overall, our work adds to emerging literature showing that modifiable lifestyle factors, specifically nutrition, have an association with male fertility potential,” said Attaman. “What is really significant is that this is the first study to show this specific relationship.”

The study was performed at Massachusetts General Hospital and involved men presenting to a fertility clinic for evaluation, some of whom had normal sperm levels and others with impaired semen quality. Men submitted a semen sample to be analyzed and then filled out a questionnaire about their intake of particular fats.

Researchers then examined the relationship between these two pieces of data and found a relationship between increased fat saturated fat consumption and lower sperm quality.

“There are multiple areas in which we are looking to focus on furthering this research,” said Attaman. “In particular, I would like to see how these findings apply in a population of males that are not presenting to a clinic for infertility.”

The findings were presented at the annual conference of American Society for Reproductive Medicine conference in Denver this week.